Every week, it seems, there’s a different 7-inch tablet on sale for under $100 at one discount store or another. Sometimes it’s a bottom-tier brand name like Coby or Pandigital; sometimes a Polaroid mixes in; and sometimes there’s no brand name anywhere — in the advertisement, on the box, or on the tablet itself.

With even an older iPad 2 starting at $399 and e-reader tablets hovering around $200, these cheapos can be tempting. In some cases you can manage a bargain, but you have to be wary. A list of good and bad tablets wouldn’t do much good in the quickly-changing marketplace, so here’s a guide for what to look for.

• Touchscreen: First of all, if it doesn’t say touchscreen, make sure it actually has one. Even then, not all touchscreens are equal. Resistive touchscreens work by measuring the change in electrical resistance when you press a thin film onto the actual screen. You can use any pointing device, like a stylus, pen cap, or your finger, but they’re not very sensitive, so you have to press hard. Some can technically do multitouch, the ability to detect more than one screen press at a time, but not very well.

Better tablets — meaning almost all of them — use capacitive touchscreens. Only your finger or other conductive stylus will work, but the sensitivity is much higher, making scrolling, typing, drawing, and other functions much smoother. Multitouch, if explicitly advertised, lets you pinch to zoom, assign events to three-finger gestures, etc.

Just remember this mnemonic: capacitive screens have the capacity for good multitouch, while resistive screens resist more than one finger.

• Processor: In the event you actually get some kind of information on what processor runs the tablet you’re considering, make sure it’s at the very least over 1GHz. Dual-core would be nice, but is rare in cheap tablets. The exact make and model aren’t so important.

• Wireless: Most tablets, even bargain ones, come with 802.11n Wi-Fi. If you only see 802.11g, that’s not bad; if your own router is g instead of n, it makes no difference when you’re at home. The newest wireless standard, 802.11ac, isn’t in much of anything yet, so don’t worry about trying to find it.

• Memory: This is where spec sheets get really lazy. Just like desktops and laptops, tablets have multiple pieces measured in megabytes (MB) and gigabytes (GB). There’s memory or RAM, where running programs play; there’s storage, where the programs and your files are permanently kept; there’s sometimes an expansion slot for SD or microSD cards; and tablets usually have some kind of dedicated memory chip inside where the operating system is stored. Sometimes this is part of the storage and sometimes it’s completely separate.

What’s more, some tablets designate how much space is available for apps and how much is available for pictures, video, and other files. They rarely give you all the details on the box, but as with PCs, more is generally better.

• Battery life: Don’t believe it. Just don’t ever believe it. Everyone uses their tablet differently, and every manufacturer tests battery life differently. At best it’s a rough comparative guide. Also don’t think a bigger mAh rating will get you longer life, because that’s dependent on how many amps the tablet uses.

• Connectivity: You probably can’t connect a generic USB mouse and keyboard unless the tablet has “USB Host” ports, and even then it’s iffy. Bluetooth? Now that’s the stuff.

The first commandment on your tablet should be to follow @CitizenjaQ on Twitter.